Aryl urea-thickened greases



United States Patent ARYL UREA-THICKENED GREASES Edward A. Swalron,Hammond, and Cecil G. Brannen,

Munster, Ind, assignors to Standard Oil Company, Chicago, 111., acorporation of Indiana N0 Drawing. Application November 18, 1953, SerialNo. 393,010

13 Claims. (Cl. 252-495) The present invention relates to novellubricant greases and to the method of preparing same. Moreparticularly, it relates to novel greases comprising a lubricant vehiclethickened with certain high melting aromatic ureido compounds. Greasesor this type, particularly those wherein the lubricant vehicle comprisesa silicone polymer oil, have demonstrated exceptional stability andlubricity at elevated temperatures.

As lubricants are required to perform at higher and higher temperaturesbecause of increased speeds of engines and machines, the advent of jetpropulsion, atomic energy as a source of power, etc., it has becomeincreasingly diiiicult to prepare greases fulfilling the requirements ofsuch lubricants. In attempting to provide such greases, the art hasprogressed from the use of petroleum lubricant vehicles thickened withmetal soaps of long chain fatty acids, e. g. lithium hydroXy-stearate,to more thermally stable synthetic lubricating oils such as the aliphat-2,710,840 Patented June 14, 1955 No. 318,321 filed November 1, 1952 (ofwhich the present application is a Continuation in Part) it is disclosedthat certain very high melting aromatic ureas, di-ureas, amides, anddi-amides, all of which contain at least one 0 RNH(J radical, wherein Ris an aryl radical, and which are referred to broadly as arylcarbarnylcompounds, may be employed to thicken silicone polymer oils, as well asother known lubricant vehicles, to produce greases which are stable anddisplay excellent lubricant properties at high temperatures.particularly preferred for use in greases employed at temperatures ashigh as about 450 F., other lubricant vehicles, either natural orsynthetic, may also be thickened with these materials to produce greasesof particular utility between about 250 F. and about 400 F.

We have discovered that greases prepared with thickeners comprisingcertain mixtures of at least two different aryl substituted ureas and/or diureas may be prepared with substantially less thickener for agrease of given consistency. Thus, in accordance with the presentinvention, mixtures of aryl substituted ureas are prepared by reacting,preferably in the lubricant vehicle (in situ), (1) at least twodifierent aryl isocyanates with at least one aryl amine (monoordi-amine) or (2) at least two different aryl monoamines with at leastone aryl isocyanate (monoor diisocyanate). Thus, in accordance herewith,we may prepare novel greases comprising an oleaginous vehicle thickenedwith mixtures of aryl substituted ureas prepared, for example, asfollows:

ic diesters of dicarboxylic acids, silicone polymers, etc., thickenedwith such soaps or inorganic materials such as silica gels. The progressof thickener research has not in general, however, kept pace with thedevelopment of lubricant vehicles. And at temperatures as high as 400 to450 F. there are tew if any greases available which will retain theirconsistency and lubricity for any substantial period of time.

In recent years various synthetic lubricant vehicles, e. g. thesilicones, fluorocarbons, etc., have been found to be potentiallyvaluable for use in greases employed at very high temperatures becauseof their thermal stability and relatively low volatility. Unless,however, a thickener having substantially the same degree of thermalstability is available to produce a grease from such an oil, they are oflittle use.

In our co-pending application for Letters Patent Serial wherein R and Rare different aryl or substituted aryl radicals. R represents an aryl,alkylaryl, substituted aryl or substituted alkylaryl radical which maybe the same as or different from R and/ or R. These radicals may difierin that one may be unsubstituted and the other substituted, or both maybe substituted but by different functional groups, e. g. by groups suchas nitro-, halo-, alkyl, sulfonyl, carbonyl, hydroxyl, amino,sulfonamido, etc. or one may be monocyclic and the other polycyclic, e.g. phenyl, diphenyl, naphthyl, etc. R and R" are different divalentarylene radicals, e. g. phenylene, biphenylene, naphthylene, etc. whichmay be substituted by such hydrocarbon or functional groups as are aboveenumerated with respect to R, R, and R. Instead of the reactants beinglimited to two amines and one isocyanate or vice versa, as shown, thereactants may comprise a plurality of both amines and isocyanates andthere may be Whereas silicone polymer oils are both monoanddisubstituted compounds of each class present in a given reaction. Thus,for example, an especially outstanding thickener may be prepared byreacting 4-biphenylyl isocyanate with p-phenylene diamine and benzidine,e. g. in a molar ratio of 4:121 respectively. To such a reaction mixturethere may be added one or more additional isocyanates, e. g.p-chlorophenyl isocyanate. Examples of other reactants and the productsobtainable therefrom will be hereinafter set forth.

The above six reactions demonstrate the manner in which mixtures ofarylureas useful in accordance herewith are preferably prepared. And, asindicated, it is preferred that such reactions be carried out in thelubricant vehicle itself. However, mixtures of ureas may likewise beprepared by reacting an individual isocyanate with an individual amineand then combining the resulting aryl substituted urea with one or moredifferently substituted ureas individually prepared. The thus preparedmixture may then be milled with a lubricant vehicle to produce a greasein accordance herewith. Mixtures of ureas prepared in this manner may beas shown above or they may comprise compounds having the formula:

( randmas R'NndNHn' wherein R, R and R" represent hydrocarbon radicalsof the type defined above.

It is a primary object of the present invention to provide lubricantgreases which are stable and give excellent lubrication at elevatedtemperatures. A further object is to provide a readily producible seriesof greases embodying a novel class of thickening agents capable ofyielding lubricants particularly suitable for use at temperatures offrom about 250 F. to about 450 F. A particular object of the presentinvention is to provide greases which are effective lubricants attemperatures as high as about 450 F. for substantial periods of time.These and addi tional objects will be apparent from the followingdetailed description.

In accordance herewith, lubricating vehicles such as silicone polymeroils, mineral lubricating oils derived from petroleum, syntheticlubricating oils such as polyalkylene glycols and their derivatives,high molecular weight esters of dicarboxylic acids, etc. and preferablythe silicone polymer oils may be thickened to grease consistency by theaddition thereto of from to 70% and preferably from about to about 50%of such mixtures of aryl substituted areas.

The possibilities of different compounds which may be produced byemploying a reaction mixture of the type above set forth is very largeand, of course, dependent upon the number and types of aryl and arylenegroups in the reactants employed. For purposes of illustration,therefore, there are hereinafter set forth a few of the various productswhich may be obtained from the reaction of such compounds as forexample 1) the reaction of phenyl isocyanate, p-tolyl isocyanate andp-aminobenzoic ac d result 5.1 the formation ofl-(p-carboxyphenyD-3-(ptolyl)-urea and p-carboxy-s-diphenyl-urea. Fromthe reaction of several amino compounds with an isocyanate,

for example, the reaction of aniline, p-toluidine and pearboxyphenylisocyanate would result in the same prod ucts as set forth above whenemploying two isocyanates and amino-benzoic acid. From the reaction oftwo isocyanates with a diamine compound, there are three expectedproducts. For example, from the reaction of pchlorophenyl isocyanate andp-tolyl isocyanate with benzidine, are produced4,4'-bis-[3-(p-chlorophenyl)-ureido]- biphenyl,4,4-bis-[3-(p-tolyl)-ureido]-biphenyl, and 4-[3-(p-chlorophenyl)-ureido]-4'-[3 biphenyl.

From the above empirical formulae, reaction equations, and the specificexamples set forth, it will be apparent to one skilled in the art thatthe products obtainable from a given set of reactants may readily bedetermined. Thus, without any intention of limiting the presentinvention to the following specific examples, there will be set forthtypical aryl isocyanates and amines as well as bifunctional isocyanatesand amines containing a bivalent aryl radical, which may be employed inaccordance herewith.

Examples of suitable aryl isocyanates which may be employed inaccordance herewith are p-chlorophenyl isocyanate, p-tolyl isocyanate,toluene diisocyanate, p-biphenylyl isocyanate (p-xenyl isocyanate),phenyl isocyanate, p-carboxyphenyl isocyanate, a-naphthyl isocyanate,p-p'-diisocyanato-biphenyl, 1,4-diisocyanato-benzene, 2-5-dichlorophenylisocyanate, o-biphenylyl isocyanate (o-xenyl isocyanate), o-chlorophenylisocyanate, p,p-diisocyanatodiphenylmethane, etc.

Example of suitable amines are p-aminobenzoic acid, p-amino-biphenyl,benzidine, dianisidine, o-tolidine, paminophenol, p-amino-benzonitrile,p-phenylene diamine, m-phenylene diamine, o-phenylene diamine,2,5-dichloroaniline, aniline, p-toluidine, etc.

As indicated above, these isocyanates and amines may be reacted invarious combinations and as long as at least two isocyanates and atleast one amine or vice versa are present, the thickener resulting fromthe reaction of these compounds will comprise a mixture of arylureas. Itis preferred to have present during the reaction a bifunctionalreactant, e. g. a diamine or a diisocyanate, but it is not necessary. Onthe other hand, more than one bifunctional material may be employed witha resulting increase in the number of possible products obtained.

The silicone polymer oils which may be employed in accordance with thepresent invention are those falling substantially within the lubricatingoil viscosity range. In general, such oils have the following unitstructure:

- (P tOlyl) ureidolwherein R and R represent substituted or unsubstituedalkyl, aryl, alkylaryl, arylalkyl or cycloalkyl radicals. Such compoundsmay be produced by well-known methods, e. g. the hydrolysis ofdialkyldichlorosilanes or dialkyldiethoxysilanes with a suitable chainstopper, e. g. a tri-substituted mono-chlorosilane. For purposes of thepresent invention, those polymers which are high boiling liquids withinthe lubricating oil viscosity range are suitable, these generallypossessing a viscosity at F. which is within the range of from about 25to about 3500 S. S. U. It is preferred, for purposes hereof, to employsuch oils as have a viscosity at 100 F. of from about 100 S. S. U. toabout 1250 S. S. U. Such products are generally colorless and inert,have a very low volatility and undergo relatively slight change inviscosity for a given change in temperature. Relatively common oils ofthis type are dimethylsilicone polymer, phenylmethylsilicone polymer,chlorophenylrnethylsilicone polymer,

etc., it being preferred to employ the phenyhnethylsilicone polymer inaccordance herewith. Methods of preparing such compounds are taught innumerous patents, e. g. U. S. 2,410,346, U. S. 2,456,496, and in theliterature such as Chemistry of the Silicones by Rochow, page 61, etseq. A particularly desirable phenylrnethylsilicone polymer for use inaccordance with the present invention is Dow-Corning 550 Silicone Fluid,a product of Dow- Corning, Inc., which has a viscosity at 100 F. ofabout 300 to about 400 S. S. U.

Other oleaginous vehicles which may be employed herewith are, forexample, mineral oils in the lubricating oil viscosity range, i. e. fromabout 50 S. S. U. at 100 F. to about 300 S. S. U. at 210 F. Thesemineral oils are preferably solvent extracted, to substantially removethe low V. I. constituents, e. g. aromatics, with phenol, furfural,B,B'-dichlorodiethy1ether (Chlorex), liquid S02, nitrobenzene, etc.Synthetic lubricating oils resulting from polymerization of unsaturatedhydrocarbons or other oleaginous materials within the lubricating oilviscosity range such as high molecular weight polyoxyalkylene compoundssuch as polyalkylene glycols and esters thereof, aliphatic diesters ofdicarboxylic acids such as the butyl, hexyl, Z-ethylhexyl, decyl,lauryl, etc. esters of sebacic acid, adipic acid, azeleic acid, etc.,may be thickened by the mixed aryl ureas of the present invention toproduce excellent greases. Polyfluoro derivatives of organic compounds,particularly hydrocarbons, in the lubricating oil viscosity range haveshown excellent promise when thickened with compounds of the presentinvention.

Greases of the present invention may be produced by one of the followingmethods:

(I) The thickener may be prepared apart from and then admixed with thelubricant vehicle and milled in a colloid mill, 3-roll mill, etc.

(2) The thickener may be formed in situ in the oil by introducing thereactants and the desired amount of lubricant vehicle, heating for arelatively short time, e. g. from about five minutes to an hour to driveoff volatile by-products, and then cooling and milling the mixture.

(3) As a slight modification of method 2 above, a solvent such aschloroform, ethyl acetate, dioxane, 2- butanone, benzene, etc. may beemployed as a diluent and mutual solvent for the reactants. The solventis then evaporated and the grease is milled, etc. substantially as setforth. Both this method and that of (2) are exceptionally useful, andresult in a saving of from 20 to 50% in thickener cost over method (1)above. (Io-pending application for Letters Patent Serial Number 392,996,filed November 18, 1953, is directed to the preparation situ technique.It is. preferred to employ this method (3) of preparation in accordanceherewith.

(4) As a step in any of the above three methods, it has been found thatimproved properties may be imparted to the grease by heat-treating thegrease mixture, i. e. subjecting the same to an elevated temperature forat least about half an hour and preferably longer, e. g. from about 1 to20 hours. Prolonged heating at such temperature may evaporate a portionof the lubricant vehicle; this loss should be replaced and then themixture should be milled. If desired, the heating and readdition ofvehicle may be repeated before milling. The temperature to which themixture may be heated will, of course, depend upon the particularlubricant vehicle employed. Thus, a silicone polymer oil may be heatedto a temperature of about 450 F. but mineral oils may only be heatedfrom about 200 to 225; diesters and other synthetic oils may be heatedsomewhat higher.

in Table 1 are set forth the data obtained on certain greases comprisingDC 550 Silicone Fluid (phenylmethyl silicone polymer oil product of DowCorning, Inc. having a methyl-phenyl ratio of about 0.6 and viscosity ofabout 300 to 400 S. S. U. at F.) thickened in accordance herewith. Thehearing test referred to in the table is a tentative one adopted by theCoordinating Research Council during the last war and is generallyreferred to as the A. B. E. C.-N. L. G. I. test. It is conducted asfollows:

3 grams of grease are placed in each of two bearings disposed on thetest spindle. One bearing, a special heat treated precision 204 KNorma-Hofiman (or Marlin-Rockwell) bearing, is subjected to atemperature of 450 F. in an oven, the other bearing, a standard NewDeparture 204 K bearing, is at a sufficiently low temperature to avoidany failure due to thermal stability of the grease. Temperature isdetermined by a thermocouple inserted in the grease between the races ofthe bearing in the oven. Failure is adjudged to occur when (1) thetemperature in the test bearing reaches 470 F. or higher, (2) Wattage inexcess of 300% of normal wattage is required, or (3) the bearing doesnot turn over at the beginning of a test cycle (the test is conducted incycles of 20 hours operating and 4 hours at rest).

In Table 2 is set forth a series of greases prepared from certainaryl-substituted urea mixtures and lubricant vehicles other thansilicone oil. Each of these greases was prepared by the above describedin situ technique, i. e. the thickeners listed were prepared in thelubricant vehicle indicated. An ethyl acetate solvent (as per method (3)supra) was employed in each case.

Table I Thickener Grease Reactants on Pergent Penetra- Method of momsThlck "tion* Before Pre (Mole) ener Amine Isoeyanate Failure -chloro henlisoc anate... (a) 1,171 (3). (1) Benzldme {g-xeny1 igooygnatef D0550 15132 {(0) 716 2-Butanone. Rename {:if3Zl;t2?Y???f?::: we 15 203 553 mm...

p-chlorophenyl isocyanate (3) (3) Benzidine p-tolyl isocyanate 3 2:222D0550 11 78 84 p-xenyl isocyanate 4 Benzidine {gjggf gfgggigi lif 1:1:1D0550 20 147 420 (1). (5) p-aminobenzoic acid {ggfi gggggg s 211:1 D655019 203 gl (6) Benzidine p-phenylene dlamiue p-xenyl isocyanate 1:114D0550 14 797 Acetate -xen lisoc anate (7) Benzldme {g-chltgophegylisocyanate D0550 12 162 632 {Dioxane.

*Kaufmann Micropenetration. A. B. E. O.N. L.

G. I. Test-the two numbers given in Example 1, i. e. (a) and (b) are theresults of two runs employing the same grease.

Table 2 Viscosity q-vi-iease, a cro- Thlckener Percent 011 2965"plenetrw st 5. tion 1,4-Bis-(3-phenylureido)-bcnzenc 4, 4, Bis (3pheny1un%i d O) bipheny1 20 Di-2-ethylhexyl sebacate 22. 2 89 1ABis-(li-phenylureido)-benzene Solvent extracted SAE 10. 7 117 4,4 -Bis-(3-phenylureido)-b1phenyl petroleum lubricating Oll. 1,4-B1s-(3-phenylurerdo)benzene.A 15 Solvent extracted S AE lo 174. 9 243 igiiszgi-tihen ilureiidtg)Lbiphenyl" petroleum lubricating oil.

1S- -p1cnyure1 o enzene. 2 is? ig i g g i? i 15 Orthoslhoate ester b. 9203 15- -p eny urei o enzenc 4:4-Bis-(3-phenylureido)-biphenyl i 10Fluomcarbon 3 6 1 In addition to the di-(2-ethylhexyl) sebaeate, whichcomprises 90.0% of the vehicle, there is present Acryloid HF825, 3.9%;phenothiazine, 0.5%; tricrcsyl phosphate, 5.0%; 1 Orsil BF-l-S (productof Oronite Chemical Corp). 3 A mixture comprising 41% "Fluorolube"silicone antifoam, 0.001%.

trifluorovinyl chloride polymer (GP-320-52) D-8433 (an experimentalproduct of Hooker Chemical Co.) and 59% of KelF-4trifluorochlorocthylene polymer (product of The M. W. Kellogg 00.).

Greases of the type set forth in Table 2 are stable at high temperaturesalthough generally somewhat less stable than those prepared withsilicone oil as the lubricant vehicle. Accordingly, they are moresuitably employed at temperatures up to about 250 F. and perhapssomewhat higher for certain individual greases, e. g. those preparedfrom fluorocarbon oils, diesters, etc. It should be understood, in anyevent, that while the greases of the present invention are particularlysuitable for use at temperatures of about 250 F. and above, they arealso extremely useful at lower temperatures. Thus, a mineral lubricatingoil derived from petroleum thickened with mixtures of aryl ureas may beemployed as multipurpose grease for automotive and industrial uses.

Whereas the mixtures of aryl-substituted ureas employed as thickenersfor lubricating vehicles in accordance herewith have been prepared ineach instance by the reaction of an amine with an isocyanate, suchmaterials may be prepared by other techniques and should be understoodthat this invention is not limited to the described method of preparingthe thickener. Thus, for example, substituted ureas of the type hereindescribed may be prepared by the reaction of an amine with an acid azideor a substituted carbamyl chloride rather than an isocyanate as hereindescribed. From the reaction of an acid azide with an amine, nitrogen isevolved while from the reaction of a carbamyl chloride with an amine,hydrogen chloride is a by-product. The evolution of hydrogen chloridehas certain disadvantages in the in situ method of producing greases andaccordingly is not recommended for use in lubricants generally. Theazide-amine reaction, however, will produce'a suitable grease thickenerwhether prepared in situ or apart from the lubricant vehicle and latermilled therewith.

Greases of the present invention may have added thereto antioxidants,oiliness agents, extreme pressure additives, etc. without in any waydeparting from the scope of the present invention.

Having thus described our invention, what we claim as novel and desireto protect by Letters Patent is defined by the following claims:

1. A lubricant grease comprising an oleaginous lubricant vehiclethickened to grease consistency with a mixture of arylureas selectedfrom the group consisting of c") 0 RNHcNHw'NH NHR' and ll RNHCNHR andmixtures thereof wherein R and R represent hydrocarbon radicalscontaining no more than 12 cyclic carbon atoms selected from the groupconsisting of aryl and substituted aryl radicals and R" is a divalenthydrocarbon 0 o v i l itNH NHR"NH NHR and 0 ll BNH NHR' and mixturesthereof wherein R and R represent different hydrocarbon radicalscontaining no more than 12 cyclic carbon atoms selected from the groupconsisting of aryl and substituted aryl radicals and R" is a divalenthydro carbon radical containing no more than 12 cyclic carbon atomsselected from the group consisting of arylcne and substituted aryleneradicals.

3. The lubricant grease of claim 2 wherein the oleaginous lubricantvehicle comprises a silicone polymer oil in the lubricating oilviscosity range.

4. The lubricant grease of claim 2 wherein the oleaginous lubricantvehicle comprises an acyclic ester of an aliphatic dicarboxylic acid inthe lubricating oil viscosity range.

5. The lubricant grease of claim 2 wherein the oleaginous lubricantvehicle comprises a mineral lubricating oil derived from petroleum.

6. The lubricant grease of claim 2 wherein the oleaginous lubricantvehicle comprises a polyfiuoro-product in the lubricating oil viscosityrange, said polyfiuoro product being a mixture of 41%trifluorovinylchloride polymer and 59% trifluorochloroethylene polymer.

7. A lubricant grease comprising a silicone polymer oil in thelubricating oil viscosity range thickened with from about 5 to about 70%by weight of a mixture of arylureas comprising 4- 3- (p-chlorophenyl)-ureido-] -4- [3 p-tolyl)-ureido]-biphenyl, 4,4'-bis-[3-(pchlorophenyl)-ureidol-biphenyl, and4,4-bis-[3-(p-tolyl)-ureido]-biphenyl.

8. The lubricant grease comprising a silicone polymer oil in thelubricating oil viscosity range thickened with from about 5 to about 70%by weight of a mixture of arylureas comprising l-(p carboxyphenyl)-3-(ptolyl)- urea, and p-carboxy-s-diphenyl-urea.

9. A lubricant grease comprising an oleaginous vehicle thickened with anamount of from about 5% to 70% by weight of a mixture of arylureasmelting above about 250 F. comprising arylureas having the generalformula 0 0 l l. RNH NHRNH NHR wherein R and R represent hydrocarbonradicals containing no more than 12 cyclic carbon atoms selected fromthe group consisting of aryl and substituted aryl radicals and R" is adivalent hydrocarbon radical containing no more than 12 cyclic carbonatoms selected from the group consisting of arylene and substitutedarylene radicals.

10. A lubricant grease comprising an oleaginous vehicle thickened withan amount of from about to about 70% by Weight of a mixture of arylureasmelting above about 250 F. comprising arylureas having the generalformula O O RNHi JNHlVNHiiNHR and and mixtures thereof wherein R and Rrepresent difierent hydrocarbon radicals containing no more than 12cyclic carbon atoms selected from the group consisting of aryl andsubstituted aryl radicals and R" is a divalent hydrocarbon radicalcontaining no more than 12 cyclic carbon atoms selected from the groupconsisting of arylene and substituted arylene radicals.

12. The method of ciairn 11 wherein the lubricant vehicle is a siliconepolymer oil in the lubricating oil viscosity range and said siliconepolymer oil and said aryl compound are heated to a temperature betweenabout 400 F. and 450 F. for a period of from about /2 hour to about 72hours.

13. A lubricant grease comprising a silicone polymer oil in thelubricating oil viscosity range thickened with from about 5 to about byweight of a mixture of arylureas comprising a'4-[3-(p-chlorophenyl)-ureido]- 4'- [3- (4-biphenylyl) -ureido -biphenyl,4,4'-bis- 3-p-chlorophenyl)-ureido]-biphenyl, and 4,4-bis-[3-(4-biphenylyl -ureido] -biphenyl.

No references cited.

1. A LUBRICANT GREASE COMPRISING AN OLEAGINOUS LUBRICANT VEHICLETHICKENED TO GREASE CONSISTANCY WITH A MAXTURE OF ARYLUREAS SELECTEDFROM THE GROUP CONSISTING OF